Heater suitable for gaseous fluids



Patented Dec. 20', 1932 UNITED STATES PATENT OFFICE ALEXANISRE FOLLIETAND NICOLAS SAINDERICHIK, F PARIS, FRANCE HEATER SUITABLE FOR GASEOUSFLUIDS Application filed December 26,.1930, Serial No. 504,818, and inTrance' December 80, 1929.

This invention relates to heaters suitable for gaseous fluids. At thepresent time, many different kinds of apparatus are known for heatingair or reheating or superheating steam, but in general such apparatuscomprises banks of tubes traversed by the gases to be heated and placedin a chamber through which gaseous products of combustion pass.

Apart from the devices used for facilitating the transfer of heat, (suchfor example as the use of refractory masses inside the tubes)difliculties are experienced in uni; formly dividing the flow of gaseousfluid to be heated or to be superheated through a large number of tubesin parallel.

Moreover, arising from the actual construction of such apparatus, thedistribution of the heating medium through the apparatus is veryirregular, this disadvantage bein particularly noticeable in the latestforms 0 apparatus employing gas or oil burners.

The use of refractory tubes, such as fused quartz, was abandoned at anearly stage of develo ment on account of their fragilit at the di erentworking temperatures, and t eir very low coefficient of thermalconductivity. The use of calorized steel tubes, special cast irons,chromed tubes, and so forth, led to an improvement from the point ofview of strength and duration, but did not permit a high temperature anda satisfactory thermal efliciency to be obtained in a manner bothpractical and economical.

Considerableprogress, especially from the point of-view of efiicientutilization of the available heating surface was made, especially in thesuperheating of steam, when the tubes instead of being traversed inparallel, were traversed successively in series.

Nevertheless, no real solution has been found to the problem of heatinggases continuously and uniformly and with aghigh thermal efliciency to atemperature of 800 C. or more without deterioration in the strength ofthe tubes.

With the object of overcoming such difiiculties, the present inventionconsists in fluidheating apparatus comprising the combinaline 4 -4: ofFigures '1 and 2 and v tion of elements hereinafter described andparticularly pointed out in the claims.

The accompanying drawing illustrates a form of construction of theinvention by way of example inwhich use is made of weldless steel tubesbent as shown and traversed by the hot gases in two sets in parallel,the fluid to be heated (air or other gas or steam) passing in successionfrom the coldest to the hottest part of each set of tubes.

Figure 1 is a longitudinal sectional elevation, showing the devices foradmitting and burning the heating gases and the means by which the upperpart of one tube communicates with its neighbour;

Figure 2 is a vertical section taken on the line-,22 of Figure 1,showing in side view the shape of the curved tubes, the tube headers,and the apertured plate for the production of thin sheets of gas in thespaces between the suspended tubes;

Figure 3 is a sectional plan taken on the line 3-3 of Figure 1; whilefinally Figure 4 is a sectional plan taken on the Figure 5 a sectionalplan on the line 5-5 p of Figure 1, of the last chamber communicatingwith the chimney.

According to'the formshown, the gases to be heated enter the apparatusthrough the inlet, 2, and after reaching a high temperature, leave bythe outlet, 3, traversing in their passage the tubes, 4, curved as shownand arranged in two sets in parallel.

In the example under description, fuel is burned on the grate, 5, theroducts of combustion passing from the urnace, 6, to the adjoiningchamber, 7, to receive a first supply of secondary air by Way of thevalve, 8, and duct, 9.

Alternatively, if desired, the grate, 5, may be replaced by burnersusing coke-oven or other gas, or by heavy-oil burners.

From the chamber, 7, the heating gases pass through the plate, 10,provided with narrow slots,11, arranged parallel to onegases risebetween the rows of 'tubes, 4, in 9 the form of thin sheets of gasproducing a maximum heating eifect on the surfaces of the tubes, 4,without directly impinging thereon.

' A further supply of secondary air is in-', troducedby way of thevalve, 12, and refractory tubes, 13, the upper. part of the latter beingprovided with transverse saw cuts, 14, spaced so as to alternate withthe parallel rows of tubes, 4.

2 ed from one tube to the next, so that the gases pass in series throughall the tubes of the same set, these headers being secured by anysuitable means to the bottom tube plate of the closed chambers, 17. Ifdesired, they may be replaced by any other fluid-tight device, whichconnects one tube with the next in order to obtain a circulation of thegas to be heated through each of the tubes in succession of the sameset.

It will be noted (see Figures 1, 3 and 5) that the groups of tubes, 4,in the heating chambers are connected by U-s haped stirrup connections,20, to the'right-hand flue, 18,

5(forming a heat-insulated chamber) and to the left-hand chamber, 19,leading. to the chimney.

The course of the heating gases after passing through the slotted plate,10, is thus up.- wards through the chamber, 21, where combustion ispractically completed, through top connecting duct, 22, downwardsthrough chamber, 23, through bottom connecting duct, 24, upwards throughchamber, 25, through top connecting duct, 26, and downwards throughleft-hand chamber, 19, and so through the duct, 27, to the chimney.

The heating gases therefore move on the whole from right to left.

The gases to be heated, on the contrary, pass in parallel through thetwo sets of tubes, 4, on the whole from left to right, communicationbetween the tubes, 4, in adjacent chambers being effected by theconnectingpipes, 28, 29and 30 as shown."

By virtue of the arrangement described above, the tubes with the headerto which they are attached can be quickly removed for repairs. As theends of the tubes are rolled into the bottom tube plate of the header,or otherwise secured thereto, the tubes and headers can be removed as aunit, and with a complete spare unit available a change can be effectedwith a minimum of delay. In this way without interrupting the working ofthe apparatus, the necessary time is available for repairing orreplacing worn tubes in the unit removed.

The upper part of the apparatus and also the connections and externalportions of the tubes are covered with a layer of suitableheat-insulating material.

The object of the curves given to one of the branches of each tube, 4,is to provide a large heatingsurface in a series of vertical parallelplanes and to obtain as uniform a heating as possible of the gas passingthrough these bends.

The invention-is, however, in no way limited to this particular way ofbending one of the branches of each tube, 4, and any other curves in avertical plane may be adopted without departing from essentialprinciples of the invention.

In accordance with the present invention, it will be seen that the gasesor vapours to be heated pass in succession through all the tubes of aset and are heated gradually and uniformly while their velocityincreases correspondingly,their maximum temperature being attained whenthey reach the righthand end chamber.

The eflective thermal efiiciency of such an apparatus is very high, onaccount of the large tube surface disposed in vertical paralll planesand subjected to the energetic heat radiation of the thin sheets ofburning gas, while at the same time the difl'erence between thetemperature of the heating gases and that of the gases to be heated, itmay be c to 800 C. or more, is always less than 200 C.

The leaving temperature of the heating gases, measured at the damper atthe foot of the chimney, is of the order of 150 C. in the case of airheated to 800 Q.

We claim: 1. Fluid-heating apparatus, comprising in combination a seriesof tubes arranged in parallel vertical planes and spaced apart tocontain the fluid to be heated, and means disposed below said tubes 'forintroducing between said tubes and without contact therewith thin movingsheets of a heated gaseous medium to heat said tubes by radiation, saidintroducing means including a plate and a series of slot-like nozzlesalternating in position with said vertical planes.

' 2. Fluid-heating apparatus comprising the combination of elementsclaimed in claim 1, together with a furnace, gaseous products from whichserve as said gaseous heating medium and means for adding air to saidgaseous products at a certain distance from said introducing means, saidadding means having spaced. air-supplying deliveries coinciding inposition with said thin gaseous sheets.

Fluid-heating apparatus comprising the combination of elements claimedin claim 1, 7

together with a furnace, gaseous products from which serve as saidgaseous heating medium and means for adding air to said gaseous productsat a certain distance from said introducing means, said adding meansincluding an air-supply duct arranged transversely of said arallelplanes and elongated apertures in said duct disposed parallel to saidparallel planes, said apertures coinciding in position with said thingaseous sheets and delivering air in the upward direction in which saidthin gaseous sheets flow.

4. Fluid heating apparatus comprising the combination of elementsclaimed in claim 1, in which said slot-like nozzles converge to a Widthless than the clear distance between said tubes arranged in saidparallel vertical planes.

In testimony whereof we have signed our names to this specification.

ALEXANDRE FOLLIET. NICOLAS SAINDERICHIN.

